ZigzagNeighbors.java

// Requires Math.floor if you don't have it already
import java.lang.Math.floor;

// [...]

// Loop in a diamond (that will be converted to zig-zag)
for (int y = -1; y <= 1; y++)
{

    // X side of the diamond
    for (int x = -1; x <= 1; x++)
    {
        
        // if this is the node we are on then skip it
        if ((x==0) && (y==0))
        {
            continue;
        }

        // Convert diamond-x to zig-zag x (relatively) - a rotation and offset for odd rows
        int dx = Math.floor((x - y + (current.y&1)) / 2);
        int dy = x + y;

        int xp = dx + current.x;
        int yp = dy + current.y;
        
        // The rest
        
    }
    
}